The present invention relates to portable radio receivers such as paging receivers, and more particularly to a portable radio receiver having a built-in antenna, whose electrical parts are arranged close to the antenna.
A receiver of this kind has a built-in loop antenna made of a metal plate as disclosed in the U.S. Pat. No. 4,123,756 assigned to the present assignee and issued on Oct. 31, 1978 or in the U.S. Pat. No. 3,956,701 assigned to Bell & Howell Co. and issued on May 11, 1976. The loop antenna generally contains the receiver's constituent parts (for example, electrical parts and printed circuit substrates, including a metal member). In such an arrangement, if a metal member maintained at an equipotential in a high frequency operation to the grounded end of the antenna is disposed close to the ungrounded end of the antenna, the effective aperture area of the loop antenna is reduced to result in a drop in the antenna gain. Though the loop aperture area can be expanded by positioning the loop antenna farther from this metal member to increase the antenna gain, it would result in a larger receiver casing, which would pose a grave problem especially to a miniature radio receiver, such as a paging receiver.